Loop type heat pipe and waste heat recovery device

ABSTRACT

A loop type heat pipe includes an evaporator located to evaporate a refrigerant by heat-exchanging with a first fluid as a heat source, and a condenser located to liquefy and condense the evaporated vapor refrigerant by heat-exchanging with a second fluid to be heated. The condenser has a refrigerant condensation side on which the condensed liquid refrigerant flows, and a refrigerant un-condensation side on which the vapor refrigerant before being condensed flows. In addition, the loop type heat pipe is provided with a flow limitation portion for flowing the second fluid from the refrigerant condensation side toward the refrigerant un-condensation side. For example, the loop type heat pipe is suitably used for a waste heat recovery device.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2006-165177filed on Jun. 14, 2006, the contents of which are incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a loop type heat pipe, in which arefrigerant is evaporated by heat from a first fluid as a heat source,and the evaporated vapor refrigerant is cooled by a second fluid to beheated so as to heat the second fluid by condensation latent heat of thevapor refrigerant. For example, the loop type heat pipe can be suitablyused for a waste heat recovery device.

2. Description of the Related Art

Conventionally, a loop type heat pipe is described in JP-A-4-45393, forexample. This loop type heat pipe is provided with an evaporator forheating and evaporating refrigerant, and a condenser for cooling andcondensing the evaporated vapor refrigerant. Furthermore, operation ofthe loop type heat pipe is controlled by a switching valve (opening andclosing valve). The switching valve is located to open and close apassage through which the liquid refrigerant condensed in the condenserreturns to the evaporator. Furthermore, the loop type heat pipe isprovided with a liquid refrigerant storage portion for storing theliquid refrigerant therein at an upstream side (i.e., condenser side) ofthe switching valve. In addition, the liquid refrigerant storage portionand the switching valve are located outside of the condenser.

The condenser is located in a tank in which the second fluid to beheated flows, such that the vapor refrigerant introduced to thecondenser is heat-exchanged with the second fluid flowing in the tank soas to heat the second fluid. However, in this loop type heat pipe, it isdifficult to always improve heating performance of the second fluid tobe heated, by a simple structure.

SUMMARY OF THE INVENTION

In view of the foregoing problems, it is an object of the presentinvention to provide a loop type heat pipe, which can effectivelyimprove heat pump efficiency.

It is another object of the present invention to provide a waste heatrecovery device which can effectively improve heat recovery efficiency.

According to an example of the present invention, a loop type heat pipein which a refrigerant circulates, includes an evaporator located toevaporate the refrigerant by heat-exchanging with a first fluid as aheat source, and a condenser located to liquefy and condense theevaporated vapor refrigerant by heat-exchanging with a second fluid tobe heated. The condenser has a refrigerant condensation side on whichthe condensed liquid refrigerant flows, and a refrigerantun-condensation side on which the vapor refrigerant before beingcondensed flows. Furthermore, the loop type heat pipe is provided with aflow limitation means for flowing the second fluid from the refrigerantcondensation side toward the refrigerant un-condensation side.Therefore, the condensed liquid refrigerant can be effectively cooled toa low temperature because a temperature difference between therefrigerant and the second fluid can be made larger on both therefrigerant condensation side and the refrigerant un-condensation side.Accordingly, the temperature of the liquid refrigerant to be supplied tothe evaporator can be lowered, and heat absorbing amount of therefrigerant in the evaporator can be increased. As a result, heat pumpefficiency of the loop type heat pipe can be effectively increased andthereby improving heating performance of the second fluid to be heated.

For example, a liquid refrigerant storage portion may be provided tostore the condensed liquid refrigerant. In this case, the flowlimitation means is provided for flowing the second fluid from a side ofthe liquid refrigerant storage portion toward the refrigerantun-condensation side. Furthermore, the liquid refrigerant storageportion may be a part of the condenser.

Alternatively, an operation stop means for stopping the evaporation ofthe refrigerant in the evaporator may be provided. For example, theoperation stop means may be a switching valve located to open and closea passage through which the liquid refrigerant condensed in thecondenser flows to the evaporator, or may be a flow control means forcontrolling a flow amount of the first fluid flowing to the evaporator.Furthermore, the loop type heat pipe may be suitably used for recoveringwaste heat of exhaust gas from an engine. In this case, the first fluidis an exhaust gas of the engine, the second fluid is a coolant used fora coolant circuit of the engine, and the evaporator and the condenserare located to recovery waste heat from the exhaust gas.

According to another example of the present invention, a waste heatrecovery device includes: a loop-type heat pipe including an evaporatorlocated to evaporate a refrigerant by performing a heat exchange with afirst fluid, and a condenser located to cool and condense the evaporatedvapor refrigerant from the evaporator; a first fluid flowing portion inwhich the first fluid flows to perform heat exchange with therefrigerant flowing in the evaporator; a second fluid flowing portion inwhich the second fluid flows to perform heat exchange with therefrigerant flowing in the condenser; an introducing pipe forintroducing the second fluid to the second fluid flowing portion; and adischarging pipe for discharging the second fluid from the second fluidflowing portion after passing through the second fluid flowing portion.Furthermore, the condenser has a refrigerant condensation side on whichthe condensed liquid refrigerant flows, and a refrigerantun-condensation side on which the vapor refrigerant before beingcondensed flows. In addition, the introducing pipe is connected to thesecond fluid flowing portion at the refrigerant condensation side of thecondenser, and the discharging pipe is connected to the second fluidflowing portion at the refrigerant un-condensation side of thecondenser. Therefore, the condensed liquid refrigerant can beeffectively cooled to a low temperature because a temperature differencebetween the refrigerant and the second fluid can be made larger on boththe refrigerant condensation side and the refrigerant un-condensationside. Accordingly, the temperature of the liquid refrigerant to besupplied to the evaporator can be lowered, and heat absorbing amount ofthe refrigerant in the evaporator can be increased. As a result, heatrecovery efficiency (heat pump efficiency) of the waste heat recoverydevice can be effectively increased.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be morereadily apparent from the following detailed description of preferredembodiments when taken together with the accompanying drawings. Inwhich:

FIG. 1 is a schematic diagram showing a loop type heat pipe used for awaste heat recovery device, according to a first embodiment of thepresent invention;

FIG. 2 is a schematic diagram showing the waste heat recovery device fora vehicle engine, according to the first embodiment;

FIG. 3 is a schematic diagram showing a loop type heat pipe used for awaste heat recovery device, according to a second embodiment of thepresent invention; and

FIG. 4 is a schematic diagram showing a loop type heat pipe used for awaste heat recovery device, according to a third embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A first embodiment will be now described with reference to FIGS. 1 and2. In this embodiment, a loop type heat pipe is typically used for awaste heat recovery device.

First, a basic structure of the waste heat recovery device will be nowdescribed. An engine (internal combustion engine) 1 is located forgenerating a rotation output for a vehicle running by fuel combustion.The engine 1 is generally provided with a coolant circuit forcontrolling heat generated in the engine 1, and an exhaust pipe 2 fordischarging exhaust gas to atmosphere.

The coolant circuit includes a radiator circuit 3, a heater circuit 4and a waste heat recovery circuit 5. Furthermore, a catalytic converter6 for purifying the exhaust gas and the waste heat recovery device 7 arelocated in the exhaust pipe 2.

Next, the coolant circuit including the radiator circuit 3, the heatercircuit 4 and the waste heat recovery circuit 5 will be described.

A radiator 9 is located to perform heat exchange between the coolantcirculated by a water pump 8 and outside air so as to cool the coolant.A bypass passage 10, through which the coolant flows while bypassing theradiator 9, is provided in the radiator circuit 3. A thermostat 11 islocated in the radiator circuit 3.

The thermostat 11 adjusts a ratio between a coolant amount passingthrough the radiator 9 and a coolant amount passing through the radiatorbypass passage 10 such that the temperature of the coolant is controlledin a temperature range (e.g., 80° C. to 100° C.). For example, when thetemperature of the coolant is low in an engine heating time, the coolantamount supplying to the radiator bypass passage 10 is increased so as tofacilitate the engine heating operation at the engine heating time.

The heater circuit 4 is connected to the engine 1, such that the coolantflows out of the engine 1 from a position different from an engineoutlet for the radiator circuit 3, and is joined to the waste heatrecovery circuit 5 on a downstream side of the waste heat recoverydevice 7. A heater core 12 is located in the heater circuit 4 to heat afluid by using heat from the coolant. For example, the heater core 12 islocated in an air duct for a vehicle air conditioner such that airflowing in the air duct is heat exchanged with the coolant. Therefore,air to be blown into a vehicle compartment is heated by the heater core12.

The waste heat recovery circuit 5 is branched from the radiator circuit3 in a passage from the engine 1 to the radiator 9, and is joined to thewater pump 8. Therefore, the coolant is circulated in the waste heatrecovery circuit 5 by operation of the water pump 8. A water tank 13(fluid tank) provided in the waste heat recovery device 7 is connectedto a passage of the waste heat recovery circuit 5.

Next, the waste heat recovery device 7 will be described. The waste heatrecovery device 7 is located to recover heat generated from the exhaustgas (first fluid as a heat source) and to heat the coolant (second fluidto be heated) flowing in the waste heat recovery circuit 5 by using theloop type heat pipe that performs heat transport (heat pump) due torefrigerant evaporation and refrigerant condensation. In thisembodiment, the waste heat recovery device 7 heats the coolant by usingheat of the exhaust gas after passing through the catalytic converter 6.

In this embodiment, an evaporator 14 and a condenser 15 contained in atank 13 (e.g., coolant tank) are integrally formed to construct the looptype heat pipe. Furthermore, a switching valve such as a differentialpressure regulating valve 16 is located to control the operation of theloop type heat pipe in accordance with an interior pressure of the looptype heat pipe.

For example, the evaporator 14 and the condenser 15 accommodated in thetank 13 are made of an anti-corrosion material (e.g., stainless steel),and are integrally bonded using a bonding technique such as brazing.After the bonding, the differential pressure regulating valve 16 isassembled to the integrated member of the evaporator 14 and thecondenser 15, so as to form the loop type heat pipe used for the wasteheat recovery device 7.

The waste heat recovery device 7 has a sealing portion (not shown).After the interior of the waste heat recovery device 7 is vacuated and arefrigerant (operation fluid) is filled therein, the sealing portion issealed.

In this embodiment, as one example of the refrigerant, water is used.The water has a boiling point of 100° C. at 1 atm. Because the interiorof the waste heat recovery device 7 is decompressed and vacuated to, forexample, 0.01 atm, water in the waste heat recovery device 7 has aboiling point in a range of 5° C.-10° C. As the refrigerant, anoperation fluid other than water, such as alcohol, fluorocarbon, Freon,etc. may be used.

The evaporator 14 is a heat exchanger in which the exhaust gas passingthrough the exhaust pipe 2 is heat exchanged with water flowing in theevaporator 14. Any type heat exchanger, for example, a laminated-typeheat exchanger, a header type heat exchanger, a drawn-cup type heatexchanger may be used as the evaporator 14. The evaporator 14 includes aheat exchanging portion 17, a lower tank 18 and an upper tank 19.

For example, the heat exchanging portion 17 is a laminated type in whichtubes 17 a and fins 17 b are alternately laminated in a laminationdirection. The heat exchanging portion 17 is mounted on a vehicle suchthat the longitudinal direction of the tubes 17 a are directed in theup-down direction of the vehicle. The fins 17 b may be omitted in theheat exchanging portion 17. In this case, the exhaust efficiency anddurability can be improved in the heat exchanging portion 17, althoughthe refrigerant evaporation capacity is decreased.

The lower tank 18 is positioned at a lower side of the heat exchangingportion 17 when the waste heat recovery device 7 is mounted on thevehicle. The differential pressure regulating valve 16 is located in thelower tank 18, such that condensed water supplied from the differentialpressure regulating valve 16 is distributed into the tubes 17 throughthe lower tank 18. The upper tank 19 is positioned at an upper side ofthe heat exchanging portion 17 when the waste heat recovery device 7 ismounted on the vehicle, such that the evaporated vapor refrigerantrising in the tubes 17 a is collected in the upper tank 19. Theevaporated vapor refrigerant collected in the upper tank 19 isintroduced to the condenser 15.

The condenser 15 is located in the tank 13 in which the coolant flows.The tank 13 is a container, and is located such that the coolant flowsbetween the tank 13 and the evaporator 14. For example, the tank 13 isconstructed with a tank plate connected to a side surface of theevaporator 14, and a tank cup connected to the tank plate to receive thecondenser 15. A coolant introducing pipe 21 for introducing the coolantinto the tank 13, and a coolant discharging pipe 22 for discharging thecoolant after passing through the tank 13 are connected to the tank 13.

The condenser 15 is a heat exchanger in which the vapor refrigerantsupplied from the evaporator 14 is heat exchanged with the coolantflowing in the tank 13. Any type heat exchanger, for example, alaminated-type heat exchanger, a header type heat exchanger, a drawn-cuptype heat exchanger may be used as the condenser 15. In this embodiment,the condenser 15 is located on the side surface of the evaporator 14,adjacent to the evaporator 14, as shown in FIG. 1.

The condenser 15 includes a heat exchanging portion 23, a refrigerantupstream tank 24 and a refrigerant downstream tank 25. The heatexchanging portion 23 includes a plurality of tubes 23 a that arelaminated at intervals. The coolant passes through the clearancesbetween the tubes 23 a in the tank 13 to be heat exchanged with therefrigerant flowing in the tubes 23 a. Each of the tubes 23 a extendsbetween the refrigerant upstream tank 24 and the refrigerant downstreamtank 25 in parallel with the tubes 17 a of the evaporator 14. The wasteheat recovery device 7 is mounted on the vehicle such that thelongitudinal direction of the tubes 23 a of the heat exchanging portion23 is directed in the vertical direction. Fins may be located on thetubes 23 a of the heat exchanging portion 23 in order to improve heatexchanging efficiency.

When the waste heat recovery device 7 is mounted on the vehicle, therefrigerant upstream tank 24 is positioned on the upper side of the heatexchanging portion 23, and the refrigerant downstream tank 25 ispositioned on the lower side of the heat exchanging portion 23, in thisembodiment. Therefore, vapor refrigerant supplied from the upper tank 19of the evaporator 14 to the refrigerant upstream tank 24 is distributedinto the tubes 23 a to be cooled and condensed by the coolant flowing inthe tank 13. Then, the condensed liquid refrigerant from the tubes 23 ais collected to the refrigerant downstream tank 25 and is introduced tothe differential pressure regulating valve 16.

Next, the differential pressure regulating valve 16 used as an operationstop means for stopping the evaporation of refrigerant in the evaporator14 will be described. The differential pressure regulating valve 16 isone example of an opening and closing valve type, and is located in acommunication passage through which the liquid refrigerant condensed inthe condenser 15 is introduced to the evaporator 14.

When the interior pressure of the waste heat recovery device 7 isincreased to be larger than a first value, the differential pressureregulating valve 16 is closed to shut the communication between thelower tank 18 of the evaporator 14 and the refrigerant downstream tank25 of the condenser 15 so as to prevent an exceed pressure increase inthe waste heat recovery device 7. In contrast, when the interiorpressure of the waste heat recovery device 7 is decreased to be lowerthan a second value lower than the first value, the differentialpressure regulating valve 16 opens the communication passage between thelower tank 18 of the evaporator 14 and the refrigerant downstream tank25 of the condenser 15 so as to restart the waste heat recoveryoperation of the waste heat recovery device 7.

In this embodiment, the differential pressure regulating valve 16 is anopening and closing valve (switching valve) which performs thecommunication or the shutting between the refrigerant downstream tank 25of the condenser 15 and the lower tank 18 of the evaporator 14, based ona differential pressure between the interior pressure of the waste heatrecovery device 7 and the atmosphere. If the atmosphere is constant,when the interior pressure of the waste heat recovery device 7 isincreased to a valve closing pressure Pc, the communication between thelower tank 18 of the evaporator 14 and the refrigerant downstream tank25 of the condenser 15 is shut. In contrast, when the interior pressureof the waste heat recovery device 7 is decreased to a valve openingpressure Po that is lower than the valve opening pressure Pc, the lowertank 18 of the evaporator 14 and the refrigerant downstream tank 25 ofthe condenser 15 are made to be communicated with each other by thedifferential pressure regulating valve 16.

FIG. 1 shows an example structure of the differential pressureregulating valve 16. As shown in FIG. 1, the differential pressureregulating valve 16 includes a housing 26, a valve body 27, a diaphragm28 and a return spring (not shown).

The housing 26 is an approximately cylindrical member located in therefrigerant downstream tank 25, and the valve body 27 is held in thehousing 26 to be movable in an axial direction. The housing 26 has aninner space 26 a, and the inner space 26 a communicates with therefrigerant downstream tank 25 through a side port 26 b so that theliquid refrigerant in the refrigerant downstream tank 25 flows into theinner space 26 a of the housing 26 of the differential pressureregulating valve 16.

The inner space 26 a of the housing 26 communicates with the lower tank18 of the evaporator 14 through a valve open port 26 c that is openedand closed by a valve body 27. Therefore, when the valve open port 26 cis opened by the valve body 27, the liquid refrigerant in the innerspace 26 a flows into the lower tank 18 through the valve open port 26c.

The valve body 27 is held in the housing 26 to be displaceable in itsaxial direction. The valve body 27 is provided with a valve bell 27 awhich opens and closes the valve open port 26 c in accordance with adisplacement of the valve body 27 in the axial direction. The diaphragm28 is located to displace the valve body 27 in the axial direction basedon the differential pressure between the interior pressure of the wasteheat recovery device 7 and the atmosphere, and to prevent panting of thedifferential pressure regulating valve 16 by reflection operation of thediaphragm 28.

The return spring (not shown) is a spring member that biases the valvebody 27 from the atmosphere side to the valve opening direction. Byadjusting the biasing force of the return spring, the valve openpressure Po for displacing the diaphragm 28 to the valve openingdirection and the valve close pressure Pc for displacing the diaphragm28 to the valve closing direction can be adjusted.

As an example, the valve open pressure Pc is set at an interior pressureof the waste heat recovery device 7 when the operation load of theengine 1 is a half throttle load at a temperature (e.g., 70° C.) of thecoolant immediately after finishing the engine heating. Furthermore, thevalve open pressure Po is set at an interior pressure of the waste heatrecovery device 7 in an engine idling (zero load operation) at atemperature (e.g., 70° C.) of the coolant immediately after finishingthe engine heating.

Next, operation of the waste heat recovery device 7 will be described.When the engine 1 starts its operation, the water pump 8 is operatedsuch that the coolant is circulated in the radiator circuit 3, theheater circuit 4 and the waste heat recovery circuit 5. At the sametime, exhaust gas generated with the fuel combustion of the engine 1flows into the exhaust pipe 2, the catalytic converter 6 and theevaporator 14 of the waste heat recovery device 7, and then isdischarged to the atmosphere.

In this example, as the refrigerant circulating in the loop type heatpipe between the evaporator 14 and the condenser 15, water is used.Therefore, the exhaust gas from the engine 1 through the exhaust pipe 2heats water as the refrigerant within the evaporator 14 while passingthrough the evaporator 14. The water in the evaporator 14 is boiled andevaporated by absorbing heat from the exhaust gas, and the evaporatedwater vapor flows in the tubes 17 a upwardly to be collected into theupper tank 19. Then, the water vapor flows from the upper tank 19 of theevaporator 14 into the refrigerant upstream tank 24 of the condenser 15.The water vapor (refrigerant vapor) introduced into the condenser 15 iscooled and condensed by the coolant flowing in the tank 13.

Immediately after the engine 1 starts its operation, the interiorpressure of the waste heat recovery device 7 is not increased to thevalve close pressure Pc. In this case, the differential pressureregulating valve 16 is opened, thereby the condensed water cooled andcondensed in the condenser 15 returns to the lower tank 18 of theevaporator 14 through the differential pressure regulating valve 16.With this, the waste heat recovery cycle can be repeated in the wasteheat recovery device 7.

Accordingly, heat of the exhaust gas is transmitted to the refrigerant(e.g., water) in the evaporator 14. Therefore, the water as therefrigerant is evaporated in the evaporator 14 by absorbing heat fromthe exhaust gas, and heat contained in the water as the refrigerant isexhausted as condensation latent heat while being condensed so as toheat the coolant circulating in the waste heat recovery circuit 5. Here,a part of heat of the exhaust gas is transmitted to members constructingthe evaporator 14 and the condenser 15, and heats the coolant flowing inthe waste heat recovery circuit 5 via those members.

As a result, the heating of the engine 1 can be facilitated at an enginestart time, and a fuel increasing time (auto choke operation ratio) forfacilitating the engine heating can be shortened, thereby improving fuelconsumption efficiency.

When the temperature of the exhaust gas is increased in accordance withincrease of the engine load after operation of the engine 1 starts, theheat quantity of the exhaust gas for heating the water as therefrigerant in the evaporator 14 is increased, and the vapor amountgenerated in the evaporator 14 is increased thereby increasing theinterior pressure of the loop type heat pipe in the waste heat recoverydevice 7. When the interior pressure of the loop type heat pipe in thewaste heat recovery device 7 is increased to the valve close pressurePc, the differential pressure regulating valve 16 is closed, so thatcondensed water in the condenser 15 does not return to the evaporator14. Therefore, water is not supplied to the evaporator 14 from thecondenser 15, and evaporation in the evaporator 14 is reduced therebythe waste heat recovery cycle is stopped. In contrast, because thecondensation of water vapor in the condenser 15 is performed, theinterior pressure of the loop type heat pipe in the waste heat recoverydevice 7 is decreased.

When the interior pressure of the loop type heat pipe in the waste heatrecovery device 7 is reduced to the valve open pressure Po, thedifferential pressure regulating valve 16 is opened, and the condensedwater in the condenser 15 flows into the lower tank 18 of the evaporator14 through the differential pressure regulating valve 16. Therefore,water as the refrigerant is evaporated again in the evaporator 14, andthe waste heat recovery cycle is restarted.

According to the first embodiment of the present invention, the wasteheat recovery device 7 is provided with a flow limitation means forperforming a flow of the coolant from a refrigerant condensation side(i.e., a side of the refrigerant downstream tank 25) to a refrigerantun-condensation side (i.e., a side of the refrigerant upstream tank 24).Here, the refrigerant condensation side is a side on which the condensedliquid refrigerant stays or flows, and the refrigerant un-condensationside is a side on which the vapor refrigerant before being condensedstays or flows. That is, as the flow limitation means, the coolantintroducing pipe 21 for introducing the coolant into the tank 13 islocated at a most downstream side (refrigerant condensation side) of thecondenser 15 in a refrigerant flow direction, and the coolantdischarging pipe 22 for discharging the coolant after passing throughthe tank 13 is located at a most upstream side (refrigerantun-condensation side) of the condenser 15 in the refrigerant flowdirection. In this arrangement of FIG. 1, the coolant introducing pipe21 is located at a bottom portion of the tank 13, and the coolantdischarging pipe 22 is located at a top portion of the tank 13, so as toform the flow limitation means.

In the first embodiment, because the coolant introducing pipe 21 islocated at the bottom portion of the tank 13 and the coolant dischargingpipe 22 is located at the top portion of the tank 13, the coolant flowsin a direction from the refrigerant condensation side (i.e., the side ofthe refrigerant downstream tank 25) toward the refrigerantun-condensation side (i.e., the side of the refrigerant upstream tank24). Therefore, liquid refrigerant condensed in the condenser 15 can becooled by the coolant before being heated or slightly heated to have arelatively low temperature. Accordingly, the liquid refrigerant to besupplied to the evaporator 14 can be cooled to a relatively lowtemperature so as to be super-cooled.

With this, the temperature of liquid refrigerant returned to theevaporator 14 is decreased, thereby increasing a temperature differencebetween the liquid refrigerant returned to the evaporator 14 and thevapor refrigerant evaporated in the evaporator 14. Thus, it is possibleto increase the heat quantity obtained from the exhaust gas in theevaporator 14, thereby increasing heat recovery efficiency (heat pumpefficiency) in the waste heat recovery device 7.

Furthermore, in the first embodiment, the vapor refrigerant immediatelyafter being introduced to the condenser 15 has a high temperature, andits temperature is lowered as the condensation is more performed. Thatis, the refrigerant has a high temperature at the refrigerantun-condensation side (i.e., the side of the refrigerant upstream tank24), and the temperature of the refrigerant is lowered as therefrigerant moves toward the refrigerant condensation side (i.e., theside of the refrigerant downstream tank 25). In contrast, the coolantintroducing pipe 21 is located at the bottom portion of the tank 13 andthe coolant discharging pipe 22 is located at the top portion of thetank 13, so that the coolant flows in the direction from the refrigerantcondensation side (i.e., the side of the refrigerant downstream tank 25)toward the refrigerant un-condensation side (i.e., the side of therefrigerant upstream tank 24), as described above. Therefore, thecoolant having been heated by the condensed liquid refrigerant having arelative low temperature, can be further heated by the un-condensationvapor refrigerant having a relative high temperature. Accordingly, thetemperature of the coolant heated by the condenser 15 while passingthrough the tank 13 can be effectively increased.

In addition, in the waste heat recovery device 7 of the firstembodiment, the differential pressure regulating valve 16 is closed whenthe interior pressure of the loop type heat pipe in the waste heatrecovery device 7 is increased. Therefore, it can prevent the waste heatrecovery device 7 from being overheated during a high engine load in thesummer, thereby preventing the waste heat recovery device 7 from beingdamaged. Furthermore, the liquid refrigerant storage portion 29 forstoring the condensed liquid refrigerant is located in the condenser 15at a refrigerant upstream side of the valve open port 26 c of thedifferential pressure regulating valve 16. Therefore, when thedifferential pressure regulating valve 16 is closed, the amount of theliquid refrigerant stored in the liquid refrigerant storage portion 29is increased.

On the other hand, when the differential pressure regulating valve 16 isopened, the liquid refrigerant of the condenser 15 flows into theevaporator 14 by using the difference between the liquid height (liquidsurface position of the refrigerant in the condenser 15) in the liquidrefrigerant storage portion 29 and the liquid height (liquid surfaceposition of the refrigerant in the evaporator 14) of the evaporator 14.Therefore, even when the differential pressure regulating valve 16 isopened, the liquid refrigerant storage portion 29, in which condensedliquid refrigerant is stored, can be formed at a refrigerant downstreamside position of the condenser 15 and at a refrigerant upstream sideposition of the valve open port 26 c of the differential pressureregulating valve 16.

The waste heat recovery device 7 of this embodiment is provided with theliquid refrigerant storage portion 29 for storing the liquid refrigerantto the lower portion in the condenser 15, and the flow limitation meansfor flowing the coolant from the side of the liquid refrigerant storageportion 29 to the refrigerant un-condensation portion of the condenser15. Accordingly, the liquid refrigerant condensed in the condenser 15can be super-cooled by the unheated coolant or the coolant having arelative low temperature, thereby the liquid refrigerant returned to theevaporator 14 can be accurately cooled to a low temperature.

Second Embodiment

The second embodiment will be described with reference to FIG. 3. In thesecond embodiment, members having the same functions as those of theabove-described first embodiment are indicated by the same referencenumbers.

In the waste heat recovery device 7 of the above-described firstembodiment, the tubes 23 a of the condenser 15 are elongated in thevertical direction so that liquid refrigerant moves downwardly by itsweight when the waste heat recovery device 7 is mounted on a vehicle.That is, in the above-described first embodiment, the condenser 15 islocated on the side surface of the evaporator 14 such that the tubes 17a of the evaporator 14 and the tubes 23 a of the condenser 15 arearranged in parallel with each other to be elongated in the verticaldirection when the waste heat recovery device 7 is mounted on a vehicle.However, in the second embodiment, the condenser 15 is located such thatthe longitudinal direction of the tubes 23 a of the condenser 15 isapproximately perpendicular to the longitudinal direction of the tubes17 a of the evaporator 14.

As shown in FIG. 3, in a waste heat recovery device 7 of the secondembodiment, the condenser 15 is located at a top portion of theevaporator 14, such that the tubes 23 a of the condenser 15 areelongated in the vehicle horizontal direction and the tubes 17 a of theevaporator 14 are elongated in the vehicle vertical direction when thewaste heat recovery device 7 is mounted on the vehicle.

The refrigerant upstream tank 24 of the condenser 15 is connected to theupper tank 19 of the evaporator 14 to directly communicate with theupper tank 19 of the evaporator 14. The differential pressure regulatingvalve 16 is located in the refrigerant downstream tank 25 of thecondenser 15 to adjust the flow of refrigerant from the refrigerantdownstream tank 25 to the evaporator 14, similarly to theabove-described first embodiment.

An open outlet of the differential pressure regulating valve 16 isconnected to the lower tank 18 of the evaporator 14 through a liquidrefrigerant passage 31. The liquid refrigerant passage 31 may beconstructed outside of the evaporator 14 or may be constructed inside ofthe evaporator 14. When the liquid refrigerant passage 31 is constructedinside of the evaporator 14 by using a part of the tubes 17 a, a heatinsulation material is used for the tube 17 a used as the liquidrefrigerant passage 31 so that the liquid refrigerant is not evaporatedwhile passing through the liquid refrigerant passage 31.

The tubes 23 a of the condenser 15 are elongated approximatelyhorizontally when being mounted on the vehicle. Even in this case, therefrigerant inside the tubes 23 a of the condenser 15 flows to therefrigerant downstream tank 25 by the pressure of the evaporated vaporrefrigerant supplied from the refrigerant upstream tank 24, so thatcondensed liquid refrigerant is collected to the refrigerant downstreamtank 25.

Accordingly, even when the tubes 23 a of the condenser 15 are arrangedto be elongated in the horizontal direction, the liquid refrigerant tobe supplied to the evaporator 14 can be collected to a side of therefrigerant downstream tank 25 of the condenser 15. In the secondembodiment, the waste heat recovery device 7 is provided with a flowlimitation means such that coolant flows in a direction from therefrigerant condensation side (i.e., the side of the refrigerantdownstream tank 25) toward the refrigerant un-condensation side (i.e.,the side of the refrigerant upstream tank 24), similarly to theabove-described first embodiment. Specifically, the coolant introducingpipe 21 is connected to the tank 13 at the side of the refrigerantdownstream tank 25, and the coolant discharge pipe 22 is connected tothe tank 13 at the side of the refrigerant upstream tank 24 so as toform the flow limitation means.

In the second embodiment, the other parts may be made similar to thoseof the above-described first embodiment.

Third Embodiment

A third embodiment will be now described with reference to FIG. 4. Inthe above-described first and second embodiments, the differentialpressure regulating valve 16 is used as one example of the operationstop means of the waste heat recovery device 7, to open and close thecommunication passage through which the liquid refrigerant condensed inthe condenser 15 flows to the evaporator 14. However, in a waste heatrecovery device 7 of the third embodiment, as shown in FIG. 4, thedifferential pressure regulating valve 16 is not provided. In the thirdembodiment, an operation stop means for stopping evaporation of therefrigerant in the evaporator 14 is constructed without using thedifferential pressure regulating means 16. For example, a fluid controlmeans for controlling a supply amount of exhaust gas (first fluid forheating) introduced to the evaporator 14 through the exhaust gas pipe 2is provided so as to stop the evaporation of refrigerant in theevaporator 14.

For example, the fluid control means is a switching means for switchingan exhaust passage through which the exhaust gas passes through theevaporator 14. By controlling the amount of the exhaust gas passingthrough the evaporator 14 to be heat exchanged with the refrigerant byusing the fluid control means, the evaporation amount of the refrigerantin the evaporator 14 can be controlled.

Furthermore, even when the differential pressure regulating means 16described in the first and second embodiments is not provided, theliquid refrigerant to be returned to the evaporator 14 is collected to arefrigerant downstream portion of the condenser 15. Accordingly, in thethird embodiment, the waste heat recovery device 7 is provided with aflow limitation means such that the coolant (second fluid to be heated)flows in a direction from the refrigerant condensation side (i.e., theside of the refrigerant downstream tank 25) toward the refrigerantun-condensation side (i.e., the side of the refrigerant upstream tank24), similarly to the above-described first embodiment. Specifically,the coolant introducing pipe 21 is connected to the tank 13 at the sideof the refrigerant downstream tank 25, and the coolant discharge pipe 22is connected to the tank 13 at the side of the refrigerant upstream tank24 so as to form the flow limitation means.

In the example of FIG. 4, the evaporator 14 and the condenser 15 areconstructed of a drawn-cup heat exchanger. However, the evaporator 14and the condenser 15 may be constructed of the other type heatexchanger, for example, a laminated type heat exchanger and a headertype heat exchanger.

In the example of FIG. 4, the upper tank 19 of the evaporator 14 and therefrigerant upstream tank 24 of the condenser 15 are connected by avapor refrigerant passage 32, and the lower tank 18 of the evaporator 14and the refrigerant downstream tank 25 of the condenser 15 are connectedby a liquid refrigerant passage 31. However, the upper tank 19 of theevaporator 14 and the refrigerant upstream tank 24 of the condenser 15may be directly connected, and the lower tank 18 of the evaporator 14and the refrigerant downstream tank 25 of the condenser 15 may bedirectly connected. Furthermore, a throttle may be provided in a passagebetween the lower tank 18 of the evaporator 14 and the refrigerantdownstream tank 25 of the condenser 15.

In the third embodiment, the other parts may be made similar to those ofthe above-described first embodiment.

Other Embodiments

Although the present invention has been fully described in connectionwith the preferred embodiments thereof with reference to theaccompanying drawings, it is to be noted that various changes andmodifications will become apparent to those skilled in the art.

For example, in the above-described first and second embodiments, thedifferential pressure regulating valve 16 is used as an example of aswitching valve (opening and closing valve). However, as the switchingvalve, a thermo valve for opening and closing its valve in accordancewith a temperature of the coolant, an electrical valve (e.g.,electromagnetic valve) opened and closed by a control unit (ECU) basedon an operation state (e.g., a detection value, a predetermined value).

In the above-described first and second embodiments, the switching valve(e.g., the differential pressure regulating valve 16) is disposed insidethe refrigerant downstream tank 25 of the condenser 15 outside of thecondenser 15. However, the switching valve may be located under thecondenser 15. Even in this case, the switching valve is located toconstruct a part of the liquid refrigerant storage portion 29, and theflow limitation means is constructed such that the coolant flows from aside of the switching valve to a side of the refrigerant downstream tank25 of the condenser 15.

In the above-described embodiments, the exhaust gas is used as anexample of a heat source first fluid. However, the other waste heat suchas a battery waste heat, an inverter waste heat, and an intercoolerwaste heat may be used as the heat source first fluid.

In the above-described embodiments, the loop type heat pipe constructedwith the evaporator 14 and the condenser 15 is typically used for awaste heat recovery device for a vehicle. However, the loop type heatpipe of the present invention can be used for the other use for a fixedequipment, for example.

In the above-described embodiments, the exhaust gas of the engine isused as an example of a heat source fluid (first fluid), and the coolantis used as an example of a fluid to be heated (second fluid). However,any other heat source fluid may be used instead of the exhaust gas, andany other fluid used for a thermal medium for a heater may be used asthe fluid to be heated. Furthermore, as the refrigerant circulatingbetween the evaporator 14 and the condenser 15 in the loop type heatpipe, the other operation fluid may be suitably used.

Such changes and modifications are to be understood as being within thescope of the present invention as defined by the appended claims.

1. A loop type heat pipe in which a refrigerant circulates, comprising:an evaporator located to evaporate the refrigerant by heat-exchangingwith a first fluid as a heat source; a condenser located to liquefy andcondense the evaporated vapor refrigerant by heat-exchanging with asecond fluid to be heated, the condenser having a refrigerantcondensation side on which the condensed liquid refrigerant flows, and arefrigerant un-condensation side on which the vapor refrigerant beforebeing condensed flows; and a flow limitation means for flowing thesecond fluid from the refrigerant condensation side toward therefrigerant un-condensation side.
 2. The loop type heat pipe accordingto claim 1, further comprising a liquid refrigerant storage portionprovided to store the condensed liquid refrigerant, wherein the flowlimitation means is provided for flowing the second fluid from a side ofthe liquid refrigerant storage portion toward the refrigerantun-condensation side.
 3. The loop type heat pipe according to claim 2,wherein the liquid refrigerant storage portion is a part of thecondenser.
 4. The loop type heat pipe according to claim 1, furthercomprising an operation stop means for stopping the evaporation of therefrigerant in the evaporator.
 5. The loop type heat pipe according toclaim 4, wherein the operation stop means is a switching valve locatedto open and close a passage through which the liquid refrigerantcondensed in the condenser flows to the evaporator.
 6. The loop typeheat pipe according to claim 4, wherein the operating stop means is aflow control means for controlling a flow amount of the first fluidflowing to the evaporator.
 7. The loop type heat pipe according to claim1, wherein: the first fluid is an exhaust gas of an engine, generated byfuel combustion in the engine; the second fluid is a coolant used for acoolant circuit of the engine; and the evaporator and the condenser arelocated to recovery waste heat from the exhaust gas.
 8. The loop typeheat pipe according to claim 1, wherein: the evaporator includes aplurality of tubes in which the refrigerant flows, the tubes beingarranged in parallel with each other and elongated in a first direction;and the condenser includes a plurality of tubes arranged in parallelwith each other and elongated in a second direction that is parallelwith the first direction.
 9. The loop type heat pipe according to claim8, further comprising a switching valve that is located in the condenserat a lower side of the tubes of the condenser to open and close apassage through which the liquid refrigerant flows toward theevaporator.
 10. The loop type heat pipe according to claim 1, wherein:the evaporator includes a plurality of tubes arranged in parallel witheach other and elongated in a first direction; the condenser includes aplurality of tubes in which the refrigerant flows, the tubes beingarranged in parallel with each other and elongated in a second directionthat is perpendicular to the first direction; and the condenser islocated at an upper side of the evaporator.
 11. The loop type heat pipeaccording to claim 10, further comprising a switching valve that islocated in the condenser at a downstream side of the tubes of thecondenser in a refrigerant flow to open and close a passage throughwhich the liquid refrigerant flows toward the evaporator.
 12. A wasteheat recovery device comprising: a loop-type heat pipe including anevaporator located to evaporate a refrigerant by performing a heatexchange with a first fluid, and a condenser located to cool andcondense the evaporated vapor refrigerant from the evaporator; a firstfluid flowing portion in which the first fluid flows to perform heatexchange with the refrigerant in the evaporator; a second fluid flowingportion in which the second fluid flows to perform heat exchange withthe refrigerant in the condenser; an introducing pipe for introducingthe second fluid to the second fluid flowing portion; and a dischargingpipe for discharging the second fluid from the second fluid flowingportion after passing through the second fluid flowing portion, wherein:the condenser has a refrigerant condensation side on which the condensedliquid refrigerant flows, and a refrigerant un-condensation side onwhich the vapor refrigerant before being condensed flows; and theintroducing pipe is connected to the second fluid flowing portion at therefrigerant condensation side of the condenser, and the discharging pipeis connected to the second fluid flowing portion at the refrigerantun-condensation side of the condenser.
 13. The waste heat recoverydevice according to claim 12, wherein: the evaporator includes aplurality of tubes in which the refrigerant flows, the tubes beingarranged in parallel with each other and elongated in a first direction;and the condenser includes a plurality of tubes in which the refrigerantflows, the tubes being arranged in parallel with each other andelongated in a second direction that is parallel with the firstdirection.
 14. The waste heat recovery device according to claim 13,further comprising a switching valve that is located in the condenser ata lower side of the tubes of the condenser to open and close a passagethrough which the liquid refrigerant flows toward the evaporator. 15.The waste heat recovery device according to claim 12, further comprisinga flow control means for controlling a flow amount of the first fluidflowing to the evaporator.
 16. The waste heat recovery device accordingto claim 12, wherein: the evaporator includes a plurality of tubes inwhich the refrigerant flows, the tubes being arranged in parallel witheach other and elongated in a first direction; the condenser includes aplurality of tubes in which the refrigerant flows, the tubes beingarranged in parallel with each other and elongated in a second directionthat is perpendicular to the first direction; and the condenser islocated at an upper side of the evaporator.
 17. The waste heat recoverydevice according to claim 16, further comprising a switching valve thatis located in the condenser at a downstream side of the tubes of thecondenser in a refrigerant flow to open and close a passage throughwhich the liquid refrigerant flows toward the evaporator.